A phenolic resin foam is low fuming and generates very little poisonous gas, and further, this foam has an excellent flame resistance and heat resistance. Accordingly, the phenolic resin foam has recently attracted attention as a refractory heat-insulating material in the fields of construction materials and ordinary industrial materials.
Nevertheless, as is well known, since the cell membrane defining cells in the phenolic resin foam is brittle and easily broken, during or after the production of the foam, the blowing agent is dissipated from the cells, resulting in a lowering of the heat-insulation thereof.
To overcome this defect, the inventors previously proposed a phenolic resin foam formed by foaming and curing a composition comprising a liquid phenolic resin, an acidic curing agent, a blowing agent, foam stabilizer and a saccharide (see Japanese Patent Publication No. 61-238833).
The phenolic resin foam disclosed in the above patent publication is superior to the conventional phenolic resin foam from the viewpoint of the resistance to brittleness (friability), heat-insulation and stability (at normal temperature), but if the density- is reduced to reduce the weight and cost of the foam or the foam is placed in an environment wherein violent changes in the temperature occur, the heat-insulation is adversely affected, and because of this defect, the use of the foam is considerably restricted.
Therefore, a primary object of the present invention is to provide a foamable phenolic resin composition suitable for the production of a phenolic resin foam wherein the heat-insulation is not substantially influenced by the reduction of the density or changes of the ambient temperature, while the characteristics of the invention of Japanese Patent Publication No. 61-238833 are retained, and a process for the preparation of this foamable phenolic resin composition.